The present invention generally relates to a countercurrent liquid-solid contacting apparatus and, more particularly, to a countercurrent liquid-solid contacting apparatus of a so-called combination type comprised of a purifying column and a regenerating column for regenerating a purifying material used in the purifying column.
The term "combination type" herein used is to be understood as meaning a liquid-solid contacting apparatus wherein the purifying and regenerating columns are combined into a single structure. By "purifying" is meant removing of contaminant materials from the treated liquid by filtration or adsorption.
A combination type liquid-solid contacting apparatus is disclosed in the Japanese Patent Publication No. 48-21551, published for opposition on June 29, 1973. According to this publication, the conventional liquid-solid contacting apparatus comprises a filtering column and a regenerating column mounted on and in communication with the top of the filtering column through a connecting passage which extends between the top of the filtering column and the downwardly tapered bottom of the regenerating column. The filtering column has its downwardly tapered bottom in communication with a source of regenerating fluid medium under pressure, either compressed air or liquid under pressure, and a discharge port defined therein at a portion adjacent the top thereof. The connecting passage between the filtering column and the regenerating column is also in communication with the source of regenerating fluid medium under pressure. First and second switching valves are respectively disposed in a first fluid line between the bottom of the filtering column and the source of the regenerating fluid medium under pressure and in a second fluid line between the discharge port and the source of the regenerating fluid medium under pressure.
The conventional liquid-solid contacting apparatus further comprises a vertically extending guide tube having a lower end positioned inside the filtering column in alignment with and in spaced relation to the opening at the bottom of the filtering column to which the first fluid line is connected, and the other extending coaxially through the connecting passage and terminating inside the regenerating column. The guide tube has a distributor tube of a diameter larger than that of the guide tube, which is rigidly mounted on a portion of the guide tube inside the filtering column and is connected to a source of a contaminated fluid medium to be substantially purified through a supply line.
At the outset, the filtering column is completely filled with a filtering material to provide a bed of filtering material whereas the regenerating column is filled with the same type of filtering material as used in the filtering column in an amount sufficient to cause particles of the filtering material inside the regenerating column to be fluidized when the necessity arises. The filtering material inside the regenerating column fills up not only a portion of the regenerating column, but also completely fills the connecting passage.
In this conventional liquid-solid contacting apparatus of the construction described above, a substantial purification of the contaminated liquid medium is carried out by, while the first and second switching valves are closed, supplying the contaminated liquid medium into the distributor tube and, then, causing the contaminated liquid medium inside the distributor tube to flow in a direction radially outwardly of the distributor tube and diagonally upwardly through the bed of filtering material. When the filtering material inside the filtering column is contaminated and during or subsequent to the process of purification of the contaminated liquid medium taking place in the manner described above, the first valve is opened to effect the supply of the regenerating fluid medium under pressure into the filtering column. The regenerating fluid medium under pressure so supplied flows into the guide tube while entraining particles of the filtering material adjacent the bottom of the filtering column into the stream of the regenerating fluid medium under pressure, whereby the contaminated filtering particles can be transported upwardly through the guide tube into the regenerating column by the stream of the regenerating fluid medium under pressure.
During the continued supply of the regenerating fluid medium under pressure into the guide tube, suspended solids adhering to and, therefore, contaminating the filtering particles are separated from the filtering particles being not only transported through the guide tube, but also fluidized within the regenerating column, the separated suspended solids being thereafter discharged to the outside of the regenerating column together with a liquid component. Forced separation of the suspended solids from the filtering particles transported into the regenerating column can be effected by subsequently supplying the regenerating fluid medium under pressure into the connecting passage through the second fluid line while the supply of the regenerating fluid medium under pressure through the first fluid line is interrupted.